1987 was the fifth year of a six-year study evaluating the yield response of cotton to supplemental water applied by center-pivot irrigation systems in the Mississippi Delta. Irrigated and non-irrigated plots were paired, using soil pH and cation exchange capacity (CEC) values, to determine yield response. Field diaries, kept by cooperating producers, were utilized to obtain costs of production. A break-even analysis, based on costs of production and selected product prices, was used to evaluate the estimated yield response.